Temporal lobe: structure and functions
Although the brain as a whole works in a continuous interaction between the different brain areas, the studies carried out from the neurosciences show that many of the aptitudes, abilities, capacities and functions of the nervous system are especially linked to certain regions.
In this sense, the human cerebral cortex has traditionally been divided into five sections, called the lobes of the brain. One of them is the temporal lobe, fundamental brain region for fundamental skills such as speech or auditory perception, in addition to being closely linked to affectivity, memory and recognition.
Location of the temporal lobe
The temporal lobe It is located on the lower side of the brain, approximately at the height of the ears . This region is anatomically separated from the parietal lobe, which corresponds to the upper lateral zone, by the Sylvian fissure, and is in close contact with the occipital lobe. Also, it is the lobe with the greatest connection to the limbic system (together with the orbito-frontal area), thus having great influence on emotions and moods, as well as memory.
It is necessary to keep in mind that there are actually two temporal lobes, one in each cerebral hemisphere. This consideration is relevant, since some of the functions of this lobe are located in most people in a specific hemisphere. However, when due to neurological alterations a part of a temporal lobe stops functioning, these functions can be performed totally or partially by its counterpart in the opposite hemisphere.
Most relevant brain locations
Within the temporal lobe there are a large number of structures . This is so because in this area of the cerebral cortex there are many interconnections coming from different parts of the brain, some of which do not bear much resemblance to each other in terms of their functions. Actually, the concept of temporal lobe responds to criteria much more anatomical than functional, so it is natural that there are groups of nerve cells and small organs specialized in different tasks.
This causes the temporal lobe to incorporate groups of neurons in charge of performing many tasks, for example, integrating types of perceptual information that come from different senses. This is what makes it have an important role in the language, mental function in which they have to see sounds, letters, etc.
Some of the most relevant parts of the temporal lobe They are the following.
1. Auditory cortex
The primary, secondary and associative auditory cortices are located in the temporal lobe . These areas of the brain are responsible for, in addition to perceiving sounds, perform the encoding, decoding and interpretation of auditory information, being an essential element for survival and communication. In this last aspect he emphasizes his participation in the understanding of speech, which occurs in the Wernicke area.
2. Wernicke area
Within the secondary auditory area of the dominant cerebral hemisphere, which is generally the left hemisphere for the majority of the population, the Wernicke area can be found. This area is the main person in charge of understanding the language , allowing verbal communication between individuals. However, the production of language occurs in another area known as the Broca area, located in the frontal cortex.
3. Angular turn
This area is of special relevance, because it is what allows literacy . It associates visual and auditory information, allowing each grapheme to assign its corresponding phoneme and making it possible for a change in the type of data with which the brain works, from images to sounds with a symbolic component.
In people with injuries in this area, the reading is usually affected, being very slow or non-existent.
4. Supramarginal rotation
It is part of the tertiary sensitive area . This turn participates in tactile recognition, in addition to participating in the language. Thanks to it we are able to recognize the relief of letters through the fingers and associate them with sounds.
5. Temporary medial
This area, which includes the hippocampal region and several relevant cortices, participates in memory and recognition , processing the information and helping to move from short-term memory to long-term memory. The left hemisphere is in charge of verbal information, while visual patterns are stored in the right hemisphere.
It is in this area of the temporal lobe where the first lesions appear in Alzheimer's, producing its initial symptoms.
6. Area of parieto-temporo-occipital association
It is an area of association that is responsible for integrating visual, auditory and somatic perception . Among many other functions of great relevance, its participation in the perception and attention to space stands out, being able to cause his injury the suffering of a heminegligencia.
7. Area of association of the limbic system
This part of the temporal lobe is responsible for providing emotional information to perceptions , integrating emotion and perception. It also participates in memory and learning. Also, other research has shown that it also has to do with the regulation of sexual behavior and the maintenance of emotional stability.
In short, this part of the temporal lobe integrates mental processes linked to emotions and allows our experiences to leave a mark on us that goes beyond what we can explain with words.
Disorders arising from injuries in the temporal
All the areas we have seen are of great importance for the proper functioning of the human organism in general and the temporal lobes in particular.
But nevertheless, it is not uncommon for accidents, diseases and alterations to occur that can cause a malfunction of some of them. Let's see some typical disorders of the temporal lesion.
1. Cortical deafness
This disorder supposes the total loss of the auditory faculty , even though the sensory organs work correctly. That is to say, the auditory information reaches the perceptive organs, but it does not get processed by the brain, with which the perception of the sound is completely lost. This alteration is produced by the destruction of the primary and secondary auditory cortices, or the nerve pathways that access them, of both hemispheres.
As with deafness, this affectation is produced by the destruction of the primary and secondary auditory cortex, with the difference that this destruction has only occurred in one hemisphere . In this way, the hearing of the opposite ear to the hemisphere in which the injury has occurred is completely lost, but since the auditory cortices of the other hemisphere remain functional, hearing is possible through the other ear.
In cases of prosopagnosia, the affected person loses the ability to recognize faces, even of their most loved ones. The recognition of people has to occur through other ways of processing the brain.
This alteration is caused by bilateral injury in the temporoccipital area .
Caused by the affectation of the parieto-temporo-occipital association area, this disorder involves the difficulty to orient, act or respond to stimuli that occur on the opposite side with respect to the injured hemisphere . The attention towards that perceptive hemifield ceases, although the person himself can move so that the stimuli that are lost are within the reach of the functional perceptual field. It usually appears together with anosognosia, which is ignorance of the existence of an alteration.
Aphasias are understood as language disorders due to brain injury . The effects vary according to the location of the lesion, and when it affects the temporal lobe there are certain characteristic symptoms.
Of the aphasias that are produced by a lesion in the temporal highlight Wernicke's aphasia (caused by an injury in the area of the same name, in which there is a loss or difficulty in verbal understanding and repetition, which causes serious problems who suffers it), the anomic (loss or difficulty finding the name of things, produced by injuries in associative temporo-parieto-occipital areas) or the sensory transcortical (in which there are difficulties in understanding but not in repetition , being the product of injuries in associative temporo-parieto-occipital areas).
If the connection of the Wernicke area with the area of Broca, the arcuate fasciculus, is damaged, the so-called driving aphasia will be produced, in which the difficulty in repetition and a somewhat altered understanding stand out, but a good creep is maintained.
6. Antegrade amnesia
This disorder implies the inability to record new material in the memory . That is, it is impossible for the patient to recover (whether permanent or temporary incapacity) the declarative information of the activity performed after the injury.
This alteration is produced by lesion in the medial temporal lobe, especially in the hippocampus. Lesions in the left hemisphere will affect verbal information, while in the right the involvement will tend to be of other ways or nonverbal.
7. Klüver-Bucy syndrome
It is a very common disorder in dementia, such as Alzheimer's . This affectation is characterized by the presence of meekness, passivity, hyperorality, difficulties of sustained attention, disappearance of fear and hypersexuality. Occurs in medial temporal lesions bilaterally.
- American Psychiatric Association (2002). DSM-IV-TR.Diagnostic and Statistical Manual of Mental Disorders. Spanish edition. Barcelona: Masson. (Original in English of 2000).
- Baños, R. and Perpiña, C. (2002). Psychopathological exploration. Madrid: Synthesis.
- Belloch, A., Baños, R. and Perpiñá, C. (2008) Psychopathology of perception and imagination. In A. Belloch, B. Sandín and F. Ramos (Eds.) Manual of Psychopathology (2nd edition). Vol I. Madrid: McGraw Hill Interamericana.
- Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Education
- Kandel, E.R .; Schwartz, J.H .; Jessell, T.M. (2001). Principles of Neuroscience. Madrird: MacGrawHill
- Kolb, B. & Wishaw, I. (2006). Human neuropsychology Madrid: Panamericana Medical Publishing House
- Manes, F. and Niro, M. (2014). Use the brain Buenos Aires: Planet.
- Netter, F. (1989). Nervous system. Anatomy and physiology Volume 1.1. Barcelona: Salvat
- Young, P.A. & Young, P.H. (2004). Clinical and functional neuroanatomy. Barcelona: Masson